People with sensorineural hearing loss experience a number of abnormalities in auditory analysis of sound in addition to their sensitivity loss. Auditory processes such as frequency and temporal resolution are usually reduced or otherwise altered by cochlear damage, and these deficits may be exacerbated when listening to sounds at high stimulus levels. This may be partially responsible for the difficulties listeners with hearing loss have in understanding speech through their hearing-aids in the presence of background noise. The focus of this program of research is to explore the consequences of listening to sound at high amplitudes by hearing-impaired individuals, with an emphasis on speech and speech-like complex stimuli. Experiments are proposed that will examine changes in frequency resolution that occur in hearing- impaired listeners as stimulus level is increased, the influence of high presentation levels on the discrimination of spectral contrast in speech- like sounds, and sensitivity to phase structure within complex sounds due to impaired frequency resolution and high presentation levels. In addition to the psychoacoustic investigations, which are designed to provide insights into the mechanisms underlying hearing impairment, the impact of these impaired functions will be evaluated in studies directly related to aspects of speech perception by hearing-impaired listeners.